XYZ .txt File to DEM

SMD84

Posted 27 May 2011 - 03:27 AM

SMD84

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Ireland

Hi,

I have recently acquired a large .txt file containing xyz data which I would like to use to create a DEM. Can anyone offer me advice on how to go about doing this? I have access to the following software

Hans van der Maarel

Posted 27 May 2011 - 07:19 AM

Hans van der Maarel

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I have recently acquired a large .txt file containing xyz data which I would like to use to create a DEM. Can anyone offer me advice on how to go about doing this? I have access to the following software

ArcEditorMapInfo ProfessionalErdas ImagineGlobal MapperSurfer

In Global Mapper:- File -> Open Generic ASCII text file, set import type to elevation grid, the rest of the specific settings you have to make in the import options depend on the structure of your XYZ file)- Set projection- Once the data is imported you can export a DEM via File -> Export Elevation Grid Format

Charles Syrett

Posted 27 May 2011 - 11:16 AM

Charles Syrett

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541 posts

Canada

Presumably you're asking for this because your points are irregularly spaced. Different applications offer different ways of creating a grid of regularly spaced points, which is basically all a DEM is. How each application interpolates elevations for the points depends on what algorithm it uses.

Global Mapper uses a TIN (triangulated irregular network) approach, as do many others. Manifold offers DEST, a specialized TIN that works very nicely when importing contour points.

Surfer offers a wide range of interpolation methods, as well as precise controls, and the differences can be surprising. However, it just generates its own grid format (.grd), and it doesn't export to a variety of other grid formats the way Global does. But if you have both Global and Surfer, Global can open the .grd file and then export to DEM.

If you want to try Surfer's interpolators, here's what you do:

- in Surfer, File>New Plot; Grid>Data>all types, open xyz file- check data columns to ensure Z data is in correct column- choose gridding method (Kriging, or whatever)- set Grid Line Geometry so it matches original, or to suit (for resolution)- this will create a Surfer .grd file- to preview, Map>New Contour Map (or Shaded Relief Map); select grid file- to create DEM, open .grd in Global Mapper and then export

You can try this using different interpolators and then choose the one that works best for you.